Recent studies have indicated that GM3 (a ganglioside that contains a terminal -2,3 linked sialic acid residue) can mediate glycoprotein independent interactions between human immunodeficiency virus 1 (HIV-1) and dendritic cells (DCs) and can, thus, induce an envelope glycoprotein-independent capture of the virus by DCs. Many aspects of this important capture mechanism remain unknown and its systematic investigation is challenged by a lack of appropriate tools to characterize the concentration and spatial distribution of GM3 in the virus membrane and of appropriate virus model systems with clearly defined surface composition. This proposal seeks to overcome these challenges by developing new noble metal nanoparticle-based tools for investigating the role of non-virus encoded surface functionalities in the pathogenesis of HIV-1. We will take advantage of the unique electromagnetic properties of noble metal nanoparticles to quantify the - as yet unknown - surface density of GM3 and its spatial distribution on viruses derived from peripheral blood mononuclear cells (PBMCs). Quantitative information about the GM3 content in HIV-1 particles will form the basis for the implementation of artificial virus nanoparticles (AVNs) that contain a gold core wrapped in a phospholipid bilayer membrane whose lipid composition mimics that of the native virus. As artificial, engineerable nanoparticles, it is possible to tune AVN GM3 surface concentration in a systematic fashion without the risk of including any other host or virus encoded surface functionalities. The AVNs introduced herein combine the advantageous material properties of metal NPs with the programmable functionality of biological membranes, are conveniently generated in large quantities, provide large optical cross-sections in fluorescent and darkfield optical microscopy, and can be localized with high resolution in both electron and optical microscopy. AVNs are, thus, ideal tools to determine the contribution of GM3 in the capture of HIV-1 particles on DCs and will enable us to probe the probe the intricate mechanisms underlying the GM3- dependent HIV-1 invasion of DCs. The specific aims of this application are: Aim1: To define the role of GM3 in interactions of primary HIV-1 isolates with DCs using nanoparticle enabled assays Aim2: To develop artificial virus nanoparticles (AVNs) that mimic GM3-mediated HIV-1 capture Aim3: To elucidate the molecular mechanisms underlying GM3-CD169 mediated binding and uptake of HIV-1 particles within DCs using AVNs.